There is an increasing need for a low cost, low brightness filler for use in ground wood specialties and newsprint. The paper industry is showing an increasing need for a lower cost, lower brightness filler of this type which will provide comparable performance with higher cost materials prepared from silica, such as the commercial product Zeolex.RTM., a trademark of the J. M. Huber Corporation. The present invention meets this need by providing a low structure magnesium silicate pigment prepared from a low cost magnesium containing raw material which contains the mineral serpentine.
The precipitation of magnesium silicate with sodium silicate and magnesium salt is known and has been described in the literature. Specific compositions of magnesium silicate are also known and described by Vournazos, Hydraulischer und weisser Magnesiazement, Zeitschrift fur anorganische und allegemeine Chemie, 200 (1931), pp. 237-244, and Strese et al, Synthese von Magnesium-silikatgelen mit swei dimensional regelmassiger Struktut, Zeitschrift fur anorganische und allgemeine Chemie, 247 (1941), pp. 65-95. Other authors have believed the compositions of the magnesium silicate vary depending on the precipitation conditions. Thus, the composition of the final product has been described as a sodium magnesium silicate by Gmelins Handbuch der anorganischen Chemie, System 27, Mg, Teil B, Lieferung 3, Weinheim, Verlag Chemie GmbH, 1938, p. 443, and magnesium silicate, Vournazos, Hydraulischer und weisser Magnesiazement, Zeitschrift fur anorganische und allegemeine Chemie, 200 (1931), pp. 237-244, Strese et al, Synthese von Magnesium-silikatgelen mit swei dimensional regelmassiger Struktut, Zeitschrift fur anorganische und allgemeine Chemie, 247 (1941), pp. 65-95 and Hinz et al, Uber die Fallungsprodukte von Magnesiumsalz- and Wasserglas-losungen, Silikat Technik, 8 (1957), pp. 148-156.
In later work it has been shown that the molar ratio of the produced magnesium silicate is the same as the molar ratio of sodium silicate used in the precipitation, as described by Hinz et al, supra. The sodium oxide content of the final product is low if magnesium salt is in excess in the precipitation and grows with a sodium silicate excess as described by Hinz et al.
The present invention provides a magnesium silicate mineral formed by precipitation which has excellent characteristics for use as a low brightness filler for newsprint.